Ive encountered a 5 inch plank maple floor that the homeowner installed himself and insists on me staining it a darker colour. I need to know what the best way to do is. A previous experience when working for another company was disasterous however I know it can be done somehow. Please give your advice.

If you pop the grain it will take stain better

Tinting the finish, with hard to stain woods like Maple and Pine, seem to be what most pros do to get an even, color, without being splotchy.

I highly recommend attempting to talk the customer OUT of a dark stain. Maple is one of the worst woods for blotchiness and uneven staining. Show them LARGE samples on sanded wood (some floor that can be sanded clean afterwards).

ALSO point out that the dark stain will hide MUCH of the beauty of the maple, such as wavy grain or bird's eye. ALSO remind them it can cause the room(s) to have a low level of light, to MANY people, dark & dreary.
(Yeah, the Interior Desecrators call it "DRAMATIC" - and there's ALOT of DRAMA in DUNGEONS.)

If they ABSOLUTELY CAN'T LIVE WITHOUT THE DARK STAIN you must "condition" the wood. This is called different things in different trades, regions or eras. Generally it is known to wood finishers as a "wash coat" - an application of a thin sealer. The wash coat soaks into the more absorbant areas of the wood MORE, so when it dries, the stain WON'T penetrate so unevenly.

Some brands market "pre-stain" or "wood conditioner". (You don't have to pay a bunch for pricey packaging of mostly SOLVENT.) This can be shellac, lacquer, "neutral" oil sealer that is appropriately thinned to about 20% solids.

I wouldn't "POP" the grain with straight water. Besides raising the moisture content of the wood, it can ADD to the uneveness of stain, unless you MIST it VERY CONSISTANTLY. I prefer to use a 50-50 mix of alcohol and water or alcohol alone. It pops the grains less but more evenly and dries faster. Yeah it costs $8 to $10/gallon - small price for a better stain job.

If I have to make maple very dark (and I charge EXTRA to do something silly like this) I include a LITTLE stain in the wash coat in order to achieve a deeper color with less hiding the wood. I prefer to use aniline dyes, as pigments hide the wood, just like a thinned paint would. Dyes actually impart color INTO the wood fibers,(like dying cloth) not just on top.

Aniline dyes can be applied mosre than once and will progressively darken the wood. They can also be added to many finishes IF you get a product with a versatile solvent that is compatible with many materials.

If any of you floor guys have tried alcohol stains on floors, these are aniline dyes, and you know they aint easy to apply. They dry almost instantly so are very tricky to get even, but it CAN BE DONE. I have done TENS of THOUSANDS of square feet with aniline stains as this is the only stain I trust under moisture cured urethane.

Okay, I'm tired of ranting. It's past my nap time.

I agree aniline dyes are very tricky to apply on floors. I've tried and gave up because I could not get the effect I was going for. But I have also heard they are not very colorfast and bleach out easily from sunlight. I still prefer oil-based stains and the new ones out from Bona, DriFast, work very well. It's quite true that maple is a b***h to stain but I've done it. Never heard about using alcohol to pop the grain though. I guess I'll need to add that trick to my bag.